1. Field of the Invention
The present invention relates to an optical element making use of the electrowetting phenomenon and, more particularly, to an optical element such as an optical filter capable of varying an amount of transmitted light, an optical switch capable of altering an optical path (traveling direction) of incident light, or the like.
2. Related Background Art
The electrowetting phenomenon (also called electrocapillarity) is conventionally known as a phenomenon in which interfacial tension varies with application of a voltage to a liquid to cause migration or deformation of an interface. This electrowetting phenomenon will be described referring to FIGS. 22A and 22B.
In FIGS. 22A and 22B, reference numeral 501 designates a substrate electrode, 502 an insulating layer formed on the substrate electrode 501, and 503 an electroconductive liquid droplet. FIG. 22A shows a state in which no voltage is placed between the substrate electrode 501 and the droplet 503 (V=0). When a voltage (V=V0) is placed between the substrate electrode 501 and the droplet 503, as illustrated in FIG. 22B, a kind of capacitor is formed to accumulate electrostatic energy. This electrostatic energy changes the balance of surface tension of the droplet 503, whereby the shape of the droplet 503 varies from the state of FIG. 22A without application of the voltage.
The electrowetting phenomenon described is utilized in the varifocal lens disclosed in WO99/18456 and in the electrocapillary display sheet disclosed in Japanese Patent Application Laid-Open No. 9-311643. There is, however, no known example of application to the other optical elements, for example, the optical elements such as the optical filter capable of varying the amount of transmitted light, the optical switch capable of altering the optical path (traveling direction) of incident light, and so on.
An object of the present invention is to provide an optical element with a function making use of the electrowetting phenomenon, which has never been known heretofore, and, particularly, to provide an optical element such as an optical filter capable of varying the amount of transmitted light, an optical switch capable of altering the optical path (traveling direction) of incident light, or the like.
In an embodiment of the present invention for accomplishing the above object, an optical element is one suitably applicable, for example, to a variable ND filter, an apodization filter, a filter for correction for reduction of marginal light amount, and so on, which comprises a first support, a second support, a first fluid, and an electroconductive or polar, second fluid having an optical transmittance different from that of the first fluid, said first and second fluids being confined in a sealed space created between the first support and the second support, said first and second fluids being immiscible with each other, wherein by varying a voltage applied to the second fluid, the shape of an interface between the first fluid and the second fluid is altered, so as to change an amount of light passing through the optical element.
In another embodiment of the present invention an optical element is one suitably applicable, for example, to an optical switch capable of altering the optical path (traveling direction) of incident light or the like, which comprises a first support, a second support, a first fluid, and an electroconductive or polar, second fluid, said first and second fluids being confined in a sealed space created between the first support and the second support, said first and second fluids being immiscible with each other, wherein by varying a voltage applied to the second fluid, the shape of an interface between the first fluid and the second fluid is altered, so as to change an optical path of incident light entering the optical element.